158 MOLLUSCA FROM THE CRAG. 
7. CarpiuM Parxinsont, J. Sowerby. Tab. XIII, fig. 7 a—é. 
Carprum Parkinsoni. J. Sow. Min. Conch., t. xlix, 1814. 
= = Woodward. Syn. Table Brit. Foss., p. 43, 1830. 
_ — Id. Geol. of Norf., p. 43, t. ii, fig. 18, 1833. 
— — Nyst. Rech. Coq. Foss. Prov. d’Anv., p. 12, No. 48, 1835. 
a = Potiez and Mich. Cat. des Moll. de Douai, t. xi, p. 183, 1844. 
— — Nyst. Coq. Foss. de Belg., p. 186, pl. xiv, fig. 2a, 6, 1844. 
Spec. Char. Testé magna, rotundato-ovatd, vel oblique-cordatd, convexd, sub-equi- 
laterali ; antice rotundatd, postice sub-angulatd ; costis 23—32 planulatis, sub-imbricatis. 
Shell large, roundedly ovate, or obliquely heart-shaped, convex, sub-equilateral ; 
anterior side rounded, posterior sub-angulated; ribs 28—32, rather flattened, and 
slightly imbricated. 
Length, 2% inches ; height, 23 inches. 
Localities. Red Crag, Walton-on-the-Naze, Felixstow, Sutton. 
Mam. Crag? Thorpe (Woodward). 
This handsome shell appears to be restricted to the Red Crag Period, for the 
specimens recorded by Woodward were rare or fragmentary, and may have been 
accidental introductions, as my Norwich collecting friends do not appear to have met 
with it in their neighbourhood. At Walton-on-the Naze it may be procured in great 
abundance, and at that rich deposit the specimens are generally in a fine state of pre- 
servation; my largest does not exceed the above dimensions, but fragments indicate 
its having attained a magnitude of at least three inches in diameter. It somewhat 
resembles in general appearance C. Js/andicum, Linn., but differs from that species in 
the form of its ribs; it also has a resemblance to C. maculatum, Gmel., C. ventricosum, 
Brug., from the bay of Campeachy, but is never so large, and seldom of such com- 
parative dimensions, our shell being generally longer than high; it differs from 
C. edule in being less angulated or pointed, but is of a more quadrate form on the 
posterior side, although specimens in the young state are exceedingly difficult to be 
distinguished. The ribs are sometimes rounded, but more generally flattened, and are, 
in the best preserved specimens, distinctly striated, but I have never been able to 
count so many as forty, the number given as its specific character in ‘Min. Conch.,’ 
and seldom more than thirty-one; they are often regularly ornamented with dwarf 
ridges, or sub-imbrications, crossing the prominent parts, and they are more distant than 
those upon the common cockle, especially on the anterior side of the shell, where, in 
some specimens, they are often regular and distinctive ; on the posterior side these 
concentric ridges are coarser and closer together; the dental characters are prominent, 
resembling those of edule, though less strongly developed, with a proportionally 
smaller ligamental area, and the shell is thinner, in all which characters there is a 
sufficient difference to entitle this to be considered as specifically distinct. 
